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  Inkjet image forming apparatus and method of compensating for defective nozzleUSPTO Application #: 20070070100Title: Inkjet image forming apparatus and method of compensating for defective nozzle Abstract: An inkjet image forming apparatus and method of compensating for a defective nozzle in an inkjet image forming apparatus are provided. By analyzing firing states of nozzles firing ink at a compensated position, which is a position printed with the defective nozzle, and at positions adjacent to the compensated position, and by firing ink having a color different from that of the defective nozzle at the compensated position according to the firing states of the nozzles to diffuse the ink fired at the adjacent positions into the compensated position, the defective nozzle is compensated. Accordingly, the missing dot of the defective nozzle is compensated for, so that it is possible to prevent deterioration in image quality such as a white band which can be easily perceived by a user. In addition, by adjusting a firing amount or chroma of the ink fired at the compensated position or the adjacent positions, it is possible to improve a compensation effect. (end of abstract) Agent: Roylance, Abrams, Berdo & Goodman, L.L.P. - Washington,, DC, US Inventor: Terekhov Vladislav USPTO Applicaton #: 20070070100 - Class: 347009000 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20070070100. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED PATENT APPLICATION [0001] This application claims the benefit under 35 U.S.C. .sctn. 119(a) of Korean Patent Application No. 10-2005-0090708, filed in the Korean Intellectual Property Office on Sep. 28, 2005, the entire disclosure of which is incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to an inkjet image forming apparatus. More particularly, the present invention relates to an inkjet image forming apparatus capable of compensating for deterioration in image quality caused by the occurrence of a defective nozzle, and a method of compensating for the defective nozzle occurrence in the inkjet image forming apparatus. [0004] 2. Description of Related Art [0005] In general, inkjet image forming apparatuses are apparatus for forming an image by firing ink with a print head which is separated by a predetermined interval from a printing medium and which reciprocates in a direction perpendicular to a conveying direction of the printing medium. Such an inkjet image forming apparatus for forming an image by firing ink on the printing medium with the print head reciprocating in a direction perpendicular to a conveying direction of the printing medium is called a shuttle type inkjet image forming apparatus. The print head of the shuttle type inkjet image forming apparatus is provided with a nozzle unit including a plurality of nozzles for firing ink. [0006] Recently, attempts have been made to implement high speed printing by using a print head having a nozzle unit corresponding to a width of a printing medium instead of using a print head reciprocating in a width direction of the printing medium. Image forming apparatuses operating in such a manner are called line printing type inkjet image forming apparatuses. In the line printing type inkjet image forming apparatuses, the print head is fixedly disposed and only the printing medium is conveyed. Therefore, driving mechanisms of the inkjet image forming apparatus are simple, and high speed printing can be implemented. [0007] FIG. 1 is a view showing a print pattern at the time of occurrence of a defective nozzle in a conventional inkjet image forming apparatus, and FIGS. 2A to 2D are views showing a method of compensating for the defective nozzle occurrence in the conventional inkjet image forming apparatus. [0008] Referring to FIG. 1, the inkjet image forming apparatus prints an image by firing ink I on a printing medium with nozzles 82 provided with a nozzle unit 80. If some of the nozzles 82 of the nozzle unit 80 have a defect, the ink I cannot be normally fired from the defective nozzle (for example, nozzle 84), so that missing lines occur on the printing medium, as shown in the figure. Namely, if some of the nozzles 82 have a defect, the ink I cannot be fired on printing regions of the printing medium printed by the defective nozzle 84, so that white bands such as missing lines occur. Since the white bands of an image printed on the printing medium can be easily seen, the white bands severely affect printing quality. A method of compensating for the deterioration in image quality caused by such a defective nozzle is disclosed in U.S. Pat. No. 5,581,284, issued Dec. 3, 1996, to Hermanson, the entire disclosure of which is incorporated herein by reference. FIGS. 2A to 2D correspond to FIGS. 3 to 6 of U.S. Pat. No. 5,581,284. [0009] The invention disclosed in U.S. Pat. No. 5,581,284, includes a method of compensating for the occurrence of a defective nozzle in an inkjet image forming apparatus. Here, the defective nozzle denotes a missing nozzle which cannot fire ink or a nozzle which cannot normally fire ink, such as a weak nozzle of which a function has become weakened. In the invention disclosed in U.S. Pat. No. 5,581,284, in a case where defective monochrome (that is, black) nozzles (element 63 in FIG. 2A) are defective, when the defective nozzles must be used, other colors, that is, cyan, magenta, and yellow are sequentially printed on the regions which must be printed by the defective nozzles 63. The associated process is shown in FIGS. 2B, 2C, and 2D. Therefore, if the cyan, magenta, and yellow colors are printed on the same point, the black color can be represented. The process is called a process Black or a process Composite Black. However, the method cannot be used for a case where nozzles firing other color ink (that is, other than black ink) have a defect. In addition, in a case where any one of the nozzles used for compensation also has a defect, the compensation is performed with resulting colors such as red (yellow+magenta), green (cyan+yellow), and blue (cyan+magenta), that are different from the process Black, and severe detrimental effects on the print quality can result. [0010] Therefore, a need exists for an effective system and method to improve the print quality by compensating for the defective nozzle. SUMMARY OF THE INVENTION [0011] Embodiments of the present invention substantially solve the above and other problems, and provide an inkjet image forming apparatus and a method of compensating for a defective nozzle capable of improving image quality by compensating for the defective nozzle. [0012] Embodiments of the present invention also provide an inkjet image forming apparatus and a method of compensating for a defective nozzle capable of minimizing influence of a defective nozzle on image quality by overcoming limitations of conventional compensating methods wherein only black colors can be compensated. [0013] Embodiments of the present invention also provide an inkjet image forming apparatus and a method of compensating for a defective nozzle capable of prolonging the life time of a print head. [0014] According to an aspect of embodiments of the present invention, a method of compensating for a defective nozzle in an inkjet image forming apparatus having a nozzle unit for firing ink on a printing medium to print an image is provided, comprising detecting the occurrence of the defective nozzle in the nozzle unit and when the defective nozzle is detected, analyzing the firing state of nozzles firing ink at a compensated position, which is a position printed with the defective nozzle, and at positions adjacent to the compensated position. The method compensates for the defective nozzle by firing ink having a color different from that of the defective nozzle at the compensated position according to the firing states of the nozzles to diffuse the ink fired at the adjacent position or positions into the ink fired at the compensated position. [0015] In the above aspect of embodiments of the present invention, the method can further comprise, when the defective nozzle is detected, performing a maintenance operation to recover the nozzle unit to a printing standby state. [0016] In addition, the method can further comprise, after the maintenance operation is performed, detecting the continued occurrence of the defective nozzle in the nozzle unit. [0017] In addition, ink having a color equal to that of the ink fired from the defective nozzle can be fired at the adjacent position. In addition, at least one of the inks fired at the adjacent positions and the ink fired at the compensated position can have a larger firing amount than an amount of normally fired ink. [0018] In addition, ink having chroma similar to that of the ink fired from the defective nozzle can be fired at the compensated position. [0019] In addition, ink having two or more colors may be fired at the compensated position. [0020] In addition, where the defective nozzle is a black nozzle firing a black ink, black ink can be fired at the adjacent position or positions. [0021] In addition, if a black nozzle adjacent to the defective nozzle is a defective nozzle, cyan, magenta, and yellow ink can be fired at the adjacent position. Continue reading... Full patent description for Inkjet image forming apparatus and method of compensating for defective nozzle Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Inkjet image forming apparatus and method of compensating for defective nozzle patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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